scholarly journals Single Units in the Medial Prefrontal Cortex with Anxiety-Related Firing Patterns Are Preferentially Influenced by Ventral Hippocampal Activity

Neuron ◽  
2011 ◽  
Vol 71 (5) ◽  
pp. 898-910 ◽  
Author(s):  
Avishek Adhikari ◽  
Mihir A. Topiwala ◽  
Joshua A. Gordon
Keyword(s):  
Prefrontal Cortex ◽  
Medial Prefrontal Cortex ◽  
Single Units ◽  
Firing Patterns ◽  
Hippocampal Activity

scholarly journals Distributed representations of temporal stimulus associations across regular-firing and fast-spiking neurons in rat medial prefrontal cortex

2020 ◽  
Vol 123 (1) ◽  
pp. 439-450
Author(s):  
Bohan Xing ◽  
Mark D. Morrissey ◽  
Kaori Takehara-Nishiuchi
Keyword(s):  
Prefrontal Cortex ◽  
Medial Prefrontal Cortex ◽  
Functional Organization ◽  
Spiking Neurons ◽  
Burst Firing ◽  
Inhibitory Neurons ◽  
Firing Patterns ◽  
Excitatory Neurons ◽  
Fast Spiking ◽  
The Difference

The prefrontal cortex has been implicated in various cognitive processes, including working memory, executive control, decision making, and relational learning. One core computational requirement underlying all these processes is the integration of information across time. When rodents and rabbits associate two temporally discontiguous stimuli, some neurons in the medial prefrontal cortex (mPFC) change firing rates in response to the preceding stimulus and sustain the firing rate during the subsequent temporal interval. These firing patterns are thought to serve as a mechanism to buffer the previously presented stimuli and signal the upcoming stimuli; however, how these critical properties are distributed across different neuron types remains unknown. We investigated the firing selectivity of regular-firing, burst-firing, and fast-spiking neurons in the prelimbic region of the mPFC while rats associated two neutral conditioned stimuli (CS) with one aversive stimulus (US). Analyses of firing patterns of individual neurons and neuron ensembles revealed that regular-firing neurons maintained rich information about CS identity and CS-US contingency during intervals separating the CS and US. Moreover, they further strengthened the latter selectivity with repeated conditioning sessions over a month. The selectivity of burst-firing neurons for both stimulus features was weaker than that of regular-firing neurons, indicating the difference in task engagement between two subpopulations of putative excitatory neurons. In contrast, putative inhibitory, fast-spiking neurons showed a stronger selectivity for CS identity than for CS-US contingency, suggesting their potential role in sensory discrimination. These results reveal a fine-scaled functional organization in the prefrontal network supporting the formation of temporal stimulus associations. NEW & NOTEWORTHY To associate stimuli that occurred separately in time, the brain needs to bridge the temporal gap by maintaining what was presented and predicting what would follow. We show that in rat medial prefrontal cortex, the former function is associated with a subpopulation of putative inhibitory neurons, whereas the latter is supported by a subpopulation of putative excitatory neurons. Our results reveal a distinct contribution of these microcircuit components to neural representations of temporal stimulus associations.

scholarly journals Evidence of hippocampal learning in human infants

2020 ◽  
Author(s):  
C. T. Ellis ◽  
L. J. Skalaban ◽  
T. S. Yates ◽  
V. R. Bejjanki ◽  
N. I. Córdova ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Statistical Learning ◽  
Medial Prefrontal Cortex ◽  
Human Memory ◽  
Human Infants ◽  
Human Hippocampus ◽  
Hippocampal Activity

The hippocampus is essential for human memory. Thus, memory deficiencies in infants are often attributed to hippocampal immaturity. However, the functionality of the infant hippocampus has never been tested directly. Here we report that the human hippocampus is indeed active in infancy. We recorded hippocampal activity using fMRI while awake infants aged 3-24 months viewed sequences of objects. Greater activity was observed when the order of the sequence contained regularities that could be learned compared to when the order was random. The involvement of the hippocampus in such statistical learning, with additional recruitment of the medial prefrontal cortex, is consistent with findings from adults. These results suggest that the hippocampus supports the important ability of infants to extract the structure of their environment through experience.

scholarly journals Medial prefrontal cortex activity reflects ordinal retrieval modes and hippocampal activity reflects temporal context retrieval modes

2018 ◽  
Author(s):  
Puck C. Reeders ◽  
Amanda G. Hamm ◽  
Timothy A. Allen ◽  
Aaron T. Mattfeld
Keyword(s):  
Prefrontal Cortex ◽  
Episodic Memory ◽  
Medial Prefrontal Cortex ◽  
Neural Correlates ◽  
Mode Interaction ◽  
Temporal Context ◽  
Hippocampal Activity ◽  
Sequence Memory ◽  
New Evidence ◽  
Spatial Content

ABSTRACTRemembering sequences of events defines episodic memory, but retrieval can be driven by both ordinality and temporal contexts. Whether these modes of retrieval operate at the same time or not remains unclear. Theoretically, medial prefrontal cortex (mPFC) confers ordinality, while the hippocampus (HC) associates events in gradually changing temporal contexts. Here, we looked for evidence of each with BOLD fMRI in a sequence task that taxes both retrieval modes. To test ordinal modes, items were transferred between sequences but retained their position (e.g., AB3). Ordinal modes activated mPFC, but not HC. To test temporal contexts, we examined items that skipped ahead across lag distances (e.g., ABD). HC, but not mPFC, tracked temporal contexts. There was a mPFC and HC by retrieval mode interaction. These current results suggest that the mPFC and HC are concurrently engaged in different retrieval modes in support of remembering when an event occurred.Significance StatementMemory for sequences of events is a defining aspect of everyday episodic memory allowing our brain to separate unique experiences that otherwise have overlapping sensory and spatial content. Sequence memory is impaired in typical aging and in disorders such as Alzheimer’s disease. The results of the current study provide new evidence that two retrieval modes concurrently arise during sequence memory, and they have distinct neural correlates. The medial prefrontal cortex contributes to an ordinal retrieval mode, while at the same time, the hippocampus contributes a gradually-changing temporal context mode of retrieval. These data shed new light on why typical episodic memory requires both the medial prefrontal cortex and the hippocampus, and suggests a functional dissociation between the medial prefrontal cortex and hippocampus across these modes of retrieval.

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